Thermionic amplifier



1951 E. e. o. ANDERSON THERMIONIC AMPLIFIER Filed Feb. 17, 1948 ruve/vToR Patented Jan. 9, 1951 THERMIONIC AMPLIFIER Edward George Orme Anderson, West Wickham, England, assignor to John Logic Baird Limited, London, England, a British company Application February 17, 1948, Serial No. 8,956 In Great Britain December 11, 1946 Section 1, Public Law 690, August 8, 1946 Patent expires December 11, 1966 2 Claims.

This invention comprises a thermionic amplifier or valve-coupled stage in which two outputs opposed to one another in phase are obtained from a single electron stream, for example, for push-pull operation of an output apparatus.

According to the invention, this result is ob-.

tained by employing a secondary-emission valve having an anode connected to one output circuit and a'secondary-emissioncathode connected to another output circuit so that the application of a modulating voltage to an input electrode of the valve produces in the first circuit an output which is in, phase opposition to the input voltage and produces in the second circuit an output which is in phase with the input voltage. There are thus obtained from a common input two outputs which are opposite to one another in phase and which can be used for example for operating a push-pull amplifier.

The invention has a particular application to a modulation stage for modulating a cathoderay tube by applying modulation voltages of opposite sign to a modulator electrode and the cathode respectively of the cathode ray tube.

One embodiment of the invention will now be described, by way of example, with reference to the accompanying drawing, as applied to a modulation stage for modulating a cathode-ray tube.

In the arrangement illustrated diagrammatically in the drawing, V indicates a secondaryemission valve having a single input electrode or control grid I arranged to receive a video-frequency modulation voltage for controlling the beam modulation of a cathode-ray tube CRO which may form part of a television receiving system. The valve'V has a thermionic cathode 2 connected through a suitable biassing resistance R to a source of negative potential, an anode 3 connected through a load resistance Rl to a positive HT source and a secondary-emission cathode 4 connected through an output resistance' R2 to a junction between two resistances R3 and R4 which are connected in serieswith one another across the HT supply so as to form a potentiometer for applying a suitable positive DC potential to the electrode 4. The valve is also provided with a screen grid 5. The anode 3 is connected through a coupling condenser CI to a modulator electrode 6 of the cathode-ray tube and the secondary-emission cathode 4 is connected through a condenser C2 to the oathode 1 of the cathode-ray tube.

voltage and which is applied to the modulator electrode 6. It also produces a second output voltage across the resistance R2 connected to the secondary emission cathode 4, and this voltage is in phase with the input voltage and is thus opposite in phase to the voltage across the resistance RI. The second output voltage is applied to the cathode l of the cathode-ray tube so that it reinforces the effect of the output applied to the modulator electrode 6 in its beammodulating effect. 7

The output resistances RI and R2 may be of equal value so chosen as to obtain a sufliciently uniform response "over the whole band of videofrequencies.

I claim:

1. Video-frequency receiving apparatus comprising a cathode-ra tube having a cathode and modulator electrode in combination with a secondary-emission valve having an anode and. a

secondary emission cathode, two output circuits connected respectively to said anodes and secondary-emission cathode of the valve so as to obtain from a common input two outputs which are opposite to one another in phase, andmeans coupling said output circuits to the modulator electrode and the cathode of the cathode-ray tube respectively so that the two outputs reinforce one another in their beam modulating effect.

2. In a television receiver, video-frequency receiving apparatus comprising a cathode-ray tube having a cathode and a modulator electrode, a secondary-emission valve having an anode and a secondary-emission cathode, a modulation signal-input circuit to the valve, 21. first output circuit coupling the anode of the valve to the modulator electrode of the cathode- In the operation of the system, modulation of the electron stream in the valve V by the input modulation voltage appliedto the electrode lproduces an output voltage across the resistance RI which is opposite in phase to the input ray tube and a second output circuit coupling the secondary-emission cathode of the valve to the cathode of the cathode-ray tube.

EDWARD GEORGE ORME ANDERSON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name ,7 Date 1,479,779 Van .der Bijl Jan. 1, 1924 1,923,252 Brolly Aug. 22, 1933 1,997,665 Wheeler Apr. 16, 1935 2,134,094 Andrieu Oct. 25, 1938 2,214,019 Gray Sept. 10, 1940 2,214,614 Hunt Sept. 10, 1940 2,280,670 Spielman Apr. 21, 1942 2,369,631 Zanarini Feb. 13, 1945 2,434,295 Strutt Jan. 13, 1948 

